The Vascular System – Chapter 13

1. The Vascular System – Chapter 13 • The vascular system consists of arteries, veins, and capillaries through which the heart pumps blood throughout the body • Arteries – away from heart • Veins – towards the heart • Capillaries – connection between arteries and veins

2. The Vascular System – Chapter 13 • Arteries • 3 layers of tissue • Outer layer: tunica externa – very strong fibrous connective tissue • Middle layer: tunica media – smooth muscle and elastic connective tissue • Inner layer: tunica intima – endothelium (simple squamous epithelium; very smooth to prevent clotting • Smaller arteries are called Arterioles • Veins • Capillaries

3. The Vascular System – Chapter 13 • Arteries • Veins • 3 layers of tissue • Outer layer: tunica externa – very strong fibrous connective tissue • Middle layer: tunica media – smooth muscle and elastic connective tissue; thinner than in arteries • Inner layer: tunica intima – endothelium (simple squamous epithelium; very smooth to prevent clotting; this tissue has folds that form valves in the veins, primarily in the legs to prevent backflow of blood • Smaller veins are called Venules • Capillaries

4. The Vascular System – Chapter 13 • Arteries • Veins • Capillaries • Carry blood from arterioles to venules • Walls are only one cell in thickness • Extension of the endothelium (simple squamous lining if arteries and veins) • Not found in epidermis, cartilage, and the lens and cornea of the eye

6. Capillary Exchange of Gases • Gases move by diffusion – area of greater concentration to lesser • Filtration also happening with plasma (this happens at arterial end of capillaries) • Colloid Osmotic pressure “pulls” fluids back into capillaries at the venous end

8. Pathways of Circulation • Pulmonary Circulation • From Right Ventricle to pulmonary artery – branching to the left and right • The pulmonary capillaries surround alveoli of the lungs – this is where the gas exchange occurs • Systemic Circulation

9. Pathways of Circulation • Pulmonary Circulation • Systemic Circulation • From Left ventricle into the aorta, then to arterioles, capillaries, venules, veins, vena cava (superior/inferior) then back to the right atrium • The Aorta branches again and again into many smaller arteries, many of them named based on the area of the body they supply blood to

11. Hepatic Portal Circulation • Subdivision of systemic circulation in which blood from the abdominal digestive organs and spleen circulates through the liver before returning to the heart. • Second set of capillaries in the liver • Remove excess glucose from the blood and store it as glycogen • Removes alcohol from the blood before it can affect the brain functions • Acts as cleanser for the blood before reciculation

12. Fetal Circulation • No blood transfer between mother and fetus • Capillaries of mother and fetus are in close proximity in the placenta • Gases, nutrients, and wastes are exchanged via diffusion and active transport mechanisms.

14. Blood Pressure • Blood pressure is the force blood exerts against the walls of the blood vessels • Maintenance of system blood pressure • Venous return – heart can only pump blood it receives • Heart rate and force – • Peripheral resistance • Elasticity of large arteries • Viscosity of blood • Loss of blood • Hormones